The upstream Mustang Oxygen sensor in your Ford is an air fuel sensor that is mounted into your exhaust manifold. This O2 sensor is also called the primary O2 sensor, the Bank 1 sensor, O2S11 the HO2S or EFI oxygen sensor. It reads and analyzes the content of your exhaust gases, and reads the amount of hydrocarbons present. Your Mustang Oxygen Sensor then translates this into a signal that your Ford engine computer will recognize and understand.
Based on this signal your Ford Mustang will dial up or crank down the fuel delivery to your engine. Depending on the model of Ford you own, there may be more than one Mustang Oxygen Sensor in your vehicle. Today I’ll be showing you how to test the primary Mustang O2 sensor in a 1992 Ford Mustang with the 2.3 liter engine in it.
The problems with your Mustang upstream oxygen sensor can cause your Ford to run rich. An excessively rich condition in your Mustang engine can cause several problems with your Ford. Because there’s too much fuel present in your engine, there will be an excessive amount of hydrocarbons in your engine oil from piston ring blowby, and in your exhaust.
This creates two distinct and not very pleasant problems, outside of your Mustang running poorly and suffering from a lack of power. Excessive hydrocarbons in your exhaust will elevate your exhaust gas temperatures to the point your catalytic converter burns out prematurely. Hydrocarbons in your engine block from ring blowby will break down your oil viscosity and threaten the longevity of your engine bearings.
If you suspect your primary O2 sensor in your Mustang going bad, you can use this guide to test it. In order to complete this DIY testing guide, you’ll need to use a digital multimeter. To begni testing your Mustang oxygen sensor, we’ll start with the heater wires or the power to your primary O2.
Testing the Mustang Oxygen Sensor for power
To begin you’ll need to open your 2.3 liter Ford Mustang hood and locate the upstream oxygen sensor. This part is screwed into your exhaust header, and you’ll need to disconnect the primary O2 harness. Put the black lead of your multimeter on the negative battery terminal, and use the red lead to gently probe the ENGINE harness side.
You are testing the wire that leads to PIN B, and with your Mustang ignition turned to the ON position, you should have 12 volts of DC signal.
If you have power at the heater element, you will now check for the ground signal for your primary oxygen sensor heater element.
This is the wire that leads to PIN A, and if you have a ground here this means that your primary Mustang O2 sensor has what it needs to operate. The next step is to measure the resistance of the heater element. Turn the dial of your digital multimeter to read resistance or OHMS, and you’ll be testing the SENSOR side of the harness now.
Measure the Mustang O2 sensor resistance
Don’t forget that this part of the test calls for you to measure the primary oxygen sensor, not the engine harness. You need to turn the dial to read resistance and then gently probe the combination of PIN A and PIN B. If your primary Mustang Oxygen sensor is still operational, it should read between 3 to 30 Ω OHM between these two pins.
If the heater element in your Mustang O2 sensor has burned out, you’ll see an open condition or an OL error. Once you’ve completed these steps and if you find that your Mustang O2 sensor is not responding, you’ll need to replace it.
Remove your bad primary O2 sensor and install a replacement upstream oxygen sensor. Have any more questions about this DIY testing guide to your primary O2 sensor? Leave us a comment below and let us know.
